Severity: Critical
CVSS Score: 9.8
Versions of `distributed` earlier than `2021.10.0` had a potential security vulnerability relating to single-machine Dask clusters. Clusters started with `dask.distributed.LocalCluster` or `dask.distributed.Client()` (which defaults to using `LocalCluster`) would mistakenly configure their respective Dask workers to listen on external interfaces (typically with a randomly selected high port) rather than only on `localhost`. A Dask cluster created using this method AND running on a machine that has these ports exposed could be used by a sophisticated attacker to enable remote code execution. Users running on machines with standard firewalls in place, or using clusters created via cluster objects other than `LocalCluster` (e.g. `dask_kubernetes.KubeCluster`) should not be affected. This vulnerability is documented in CVE-2021-42343, and was fixed in version `2021.10.0` (PR #5427).